Get extractedGitHubUrls to work with conditional rendering

[humphd]

In #2367 we're adding GitHub info for posts, and we have included a new function, extractedGitHubUrls. We'd like to memoize this result, but our early work at doing so hasn't been successful. Here's what we think it should look like, but it needs to get fixed so it works:

  // Extract all the github urls from the post
  const extractedGitHubUrls: string[] = useMemo(
    () => (post?.html ? extractGitHubUrlsFromPost(post.html) : []),
    [post?.html]
  );
  ...
  {extractedGitHubUrls.length ? <GitHubInfo ghUrls={extractedGitHubUrls} /> : null}

cc @menghif @DukeManh

[menghif]

It currently works with useMemo as of right now. However it does not work if we change this:

{extractedGitHubUrls.length ? <GitHubInfo ghUrls={extractedGitHubUrls} /> : null}

into this:

{extractedGitHubUrls.length > 0 ?? <GitHubInfo ghUrls={extractedGitHubUrls} />}

We have used this syntax: condition && <Component/> in GitHubInfo.tsx so we would like to change it here too for consistency.

[menghif]

@humphd We can delete this, I fixed it in #2367. It was a typo ?? instead of &&. Sorry about that.

[humphd]

Awesome!